The DVU21 Joint Venture, led by Doğuş İnşaat, has completed the excavation works for Lot 4 of Sofia Metro Line 3, successfully reaching the first station.
. This marks a significant milestone in the construction of the line’s most technically complex section, which runs through densely populated urban zones with limited surface access.
“Having constructed 90% of all TBM-built metro tunnels in Sofia, we have already achieved 25% progress on this particular line,” Doğuş İnşaat says. The company has extensive international experience in tunneling and large-scale infrastructure projects, contributing to efficient project execution under challenging geotechnical conditions.
Lot 4 of Sofia Metro Line 3, known as the Slatina section, is a 5.4 km long underground line from Shipka Street and Slatina District up to Tsarigradsko Street. This section is particularly important due to its proximity to residential areas, business zones, and major city arteries, promising a substantial impact on urban mobility and quality of life.
The project involves the extension of the current Sofia Metro, Line III Lot 4 in relation with Depot “Botevgradsko Shosse” Boulevard – VI. Vazov Boulevard, Central City Area, “Ovcha Kupel” District – Lot 4: km 11+966.34 (Start Shaft) – km 5+248.57 (Exit Shaft) Construction of TBM Tunnel.
Tendered by Metropoliten EAD, the project includes a 5.67 km section with six underground stations. Upon completion, it is expected to reduce urban vehicle traffic by 30% and increase the rail system’s share in public transport to 50%, thus playing a crucial role in Sofia’s transition to sustainable, low-emission urban transport.
TBM tunneling works are scheduled for completion in Q4 2026, and the line is planned to become operational in April 2027. In addition to easing traffic congestion, the extension will improve connectivity between peripheral districts and the city center, offering a fast, safe, and environmentally friendly transport alternative.
The Line 3 will be 21 km long with 21 metro stations with branches. The first one, planned due to the big passenger flow, is in the eastern part of the line close to MS 7 in the area of Military Academy and it is directed towards Slatina RD–Tsarigradsko Shose Blvd.
Considering the large scale of the project, the various methods of construction, the specifics of the lots, and the limited financial resources, Line 3 is planned to be constructed in four stages (lots), each executed in phases to reduce disruptions and ensure financial feasibility.
The first stage was constructed from 2016 to 2020 on the Vladimir Vazov Blvd. – Center – Zhitnitsa St. route and included a 7.8 km line with 8 metro stations and a depot at the area of Zhitnitsa. For the first two lots, the project also covered the purchase of 20 modern metro trains featuring energy-efficient systems and improved passenger comfort.
The second stage (west section) included four metro stations and improved access to the southwestern districts. The third stage, with a length of 3 km, served by three stations, continues the line from Zhitnitsa St., through Ovcha Kupel to the Ring Road, easing commuting times for thousands of residents.
The third stage – a 3 km section with three stations – starts under Vladimir Vazov Blvd. at the crossing with Panayot Hitov St., to Levski, extending the service into the eastern parts of the capital.
The fourth lot starts at the entrance of the Military Academy at Evlogi and Hristo Georgievi Blvd. It passes through Geo Milev RD, Slatina RD, along the Arena Armeets to Tsarigradsko Shose Blvd. It is 6 km long with six metro stations. This section will also offer interchange opportunities with major surface transportation lines and future urban rail developments.
In addition to transportation benefits, the construction of Line 3 Lot 4 supports job creation, urban regeneration, and increased property values in the surrounding neighborhoods. Environmental impact assessments have been carried out to ensure minimal disruption to local ecosystems and compliance with EU standards.
The Sofia Metro extension remains one of Bulgaria’s most important infrastructure investments in recent decades, aligning with EU strategies for greener, smarter, and more resilient cities.
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